A leading accounting group has savaged Federal Treasurer Joe Hockey's comments on income tax cuts, accusing him of repeating rhetoric instead of fixing Australia's "broken down tax system".

Key points

Hockey says bracket creep behind push for income tax cuts

Treasurer says changes will encourage people to stay in workforce

CPA Australia says speech just recycled rhetoric

Mr Hockey made the case for income tax cuts, including for Australia's highest earners, during a speech in Sydney in which he highlighted the problem of "bracket creep".

He said the Government had to cut taxes for middle and low-income earners, saying that without the changes, almost half of all taxpayers would be in the top two tax brackets in a decade.

But Certified Practicing Accountants (CPA) Australia's Alex Malley has lashed the Government for what he called pre-election "fiscal giveaways".

"The Treasurer appears to be caught in a cycle of restating the problems rather than rethinking the solutions," Mr Malley said.

"The issue of income tax, GST, super [annuation], company tax, land tax is yet to be discussed ... it really is being deferred and deferred and deferred.

"To actually start forcing a conversation around just personal income tax says to me that we're in a downhill slide to an election and that's not good for Australia, we need to make some tough decisions.

"To defer and distract again in relation to tax and tell us what we already knew at a five-star hotel in Sydney is not my idea of leadership."

The Treasurer argued the tax changes would help economic growth.

"If people are left in those higher tax brackets ... the incentive for hard work is blunted — and inflation means that without a real wage rise, people pay a higher and higher average tax rate each year," he said.

"This is more talk from the man who's been talking about lower and fairer taxes for several years now and has delivered higher and more unfair taxes, and especially unfair spending cuts," Mr Bowen said.

"The billions of dollars of cuts that would be necessary to fund the sort of tax cuts that Joe Hockey's flagging today would come at a very significant cost.

"Joe Hockey needs to outline in much greater detail than he has in a thought bubble today, how he's going to go about this plan."

Respected economist Saul Eslake said bracket creep was an issue that needed to be addressed, but that reducing the overall tax take was hard to justify.

"While there is a good case for doing something about the likelihood, the certainty, that people will be pushed into the second top tax bracket who shouldn't be there, there is also a compelling case ... for other reforms to the tax system that will help keep the budget on a sustainable footing, as there is also a case, of course, for continued restraint in government spending," he said.